The present invention relates to a wafer cleaning device and a tray for use in the wafer cleaning device, particularly to a wafer cleaning device in which a tray containing wafers is steeped in a cleaning tank and cleaning fluid is allowed to flow to clean the wafers and to a tray for use in the wafer cleaning device.
In a conventional method of manufacturing semiconductor wafers, a cleaning process is performed to rinse the surfaces of semiconductor wafers (hereinafter referred to as wafers) in chemical liquid, pure water or another cleaning fluid. A wafer cleaning device and a tray for use in the wafer cleaning device are used in the process. To maintain the performance and reliability of wafers, the wafer cleaning device and the tray are requested to have a high cleaning capability to reduce contaminant substances adhering to the surfaces of the wafers. Especially, in a large wafer having a diameter of 12 inches (300 mm), the cleaning effect is largely changed by the flow of the cleaning fluid to be supplied to the cleaning tank, the tray for conveying the wafers, or other conditions. Moreover, for the large wafer, since the amount of cleaning fluid for use in cleaning is also increased, the capacity of the cleaning tank is one of important factors. To solve the problems, various wafer cleaning devices and trays for use in the wafer cleaning devices have been developed.
FIG. 3 is a perspective view showing a conventional wafer cleaning device. Moreover, FIG. 4 is a sectional view showing a section taken along line Bxe2x80x94B in FIG. 3.
As shown in FIG. 3, the conventional wafer cleaning device is constituted of a cleaning tank 50 for housing and cleaning wafers 40 conveyed by a conveyor robot 42, and a mounting base 52 onto which the wafers 40 conveyed by the conveyor robot 42 are arranged and mounted on the bottom of the cleaning tank 50.
When the wafer cleaning device constituted as aforementioned is used, a plurality of arranged wafers 40 are a grasped by the conveyor robot 42 in a predetermined process and conveyed to an upper part of the cleaning tank 50. After the wafers 40 are conveyed to above the cleaning tank 50, the conveyor robot 42 moves down to mount a plurality of wafers 40 onto the mounting base 52 of the cleantng tank 50. After the wafers 40 are mounted, the cleaning fluid is allowed to flow via a flow port (not shown) provided in the bottom of the cleaning tank 50, so that the wafers 40 are cleaned by the flow.
According to the wafer cleaning device constituted as described above, since the wafers 40 are constantly cleaned by the cleaning fluid when the conveyor robot 42 mounts and takes out the wafers, the wafers 40 are not contaminated by the conveyor robot 42.
In the structure of the wafer cleaning device, however, as shown in FIG. 4, a space H in which the conveyor robot 42 is steeped is necessary between the side face of the wafer 40 and the side wall of the cleaning tank 50. Therefore, as the cleaning tank is enlarged, the amount of cleaning fluid for use is also increased. Moreover, for the mounting base 52 provided on the bottom of the cleaning tank 50, the contaminant substances peeled off the wafers 40 by cleaning are deposited to disadvantageously re-contaminate newly mounted wafers. To solve the problem, there is proposed a wafer cleaning device in which wafers are housed in a tray for cleaning.
FIG. 5 is a perspective view showing such conventional wafer cleaning device and a tray for use in the wafer cleaning device. Moreover, FIG. 6 is a sectional view showing a section taken along line Cxe2x80x94C shown in FIG. 5.
As shown in FIG. 5, in the conventional wafer cleaning device and the tray for use in the wafer cleaning device, there are provided a tray 70 formed substantially in a box shape having opened top and bottom ends for containing inside a plurality of vertically arranged wafers 60, and a cleaning tank 80 for cleaning the wafers 60 in the tray 70 conveyed by a conveyor robot 62.
When the wafer cleaning device and the tray for use in the wafer cleaning device constituted as described above are used, in a predetermined process, a plurality of wafers 60 are inserted in the tray 70, and the tray 70 is grasped and conveyed to above the cleaning tank 80 by the conveyor robot 62. After the conveyor robot 62 conveys the wafers 60 to above the cleaning tank 80, the conveyor robot 62 moves down to mount the tray 70 onto the bottom of the cleaning tank 80. After the tray 70 is mounted, the cleaning fluid is allowed to flow via a flow port (not shown) provided in the bottom of the cleaning tank 80, so that the wafers 60 are cleaned by the flow.
According to the wafer cleaning device and the tray for use in the wafer cleaning device, as shown in FIG. 6, a space in which the conveyor robot 62 is steeped is unnecessary between the side face of the tray 70 and the side wall of the cleaning tank 80. By eliminating the space, the cleaning tank 80 can be miniaturized. Moreover, after cleaning is completed, the tray 70 containing the wafers 60 is removed from the cleaning tank 80, and kept constantly in a clean state, so that the wafers 60 fail to be contaminated.
In this manner, cleaning is effectively performed by preventing the wafers from being contaminated in the conventional wafer cleaning device and the tray for use in the wafer cleaning device.
However, in the conventional wafer cleaning device and the tray for use in the wafer cleaning device, since the fluid resistance of the cleaning fluid is enlarged inside the tray 70 shown in FIG. 5, the flow rate of the cleaning fluid is relatively decreased in the vicinity of the wafers. Therefore, to secure a constant flow rate necessary for the cleaning of wafers, a high flow rate is necessary in whole, and the amount of cleaning fluid for use is also disadvantageously increased.
Moreover, in the conventional wafer cleaning device and the tray for use in the wafer cleaning device, a grasping portion by which the wafers are grasped has a large contact area abutting on the wafers in the tray, and a probability of contaminating the wafers by particles and other contaminant substances is high. There is a disadvantage that the particles and other contaminant substances adversely affect production yield and remarkably deteriorate product quality.
An object of the present invention is to solve the problem described above and to provide a wafer cleaning device which prevents the contamination of wafers and which can effectively clean the wafers and a tray for use in the wafer cleaning device.
To solve the problem described above, the present invention provides a wafer cleaning device in which a plurality of wafers arranged at predetermined intervals are housed in a cleaning tank and cleaning fluid is supplied from a bottom face to clean the wafers. There is provided a tray which comprises grasping grooves formed in a band-shaped peripheral wall surrounding an outer periphery of the plurality of arranged wafers to expose upper and lower portions of the wafers for grasping opposite side ends of the arranged wafers and grasping portions by which the peripheral wall is conveyed. There is also provided a cleaning tank which comprises a guide for holding the tray in a predetermined position, a bottom face formed conforming to a bottom-face shape of the wafer, and a flow port for allowing the cleaning fluid to flow between the bottom face and wafer bottom faces.
Here, the bottom portion of the cleaning tank is formed substantially in a V-shape conforming to the bottom-face shape of the wafer, and inclined at an angle of 24 degrees relative to a horizontal plane. Moreover, the cleaning tank is further provided, on an outer side face, with an overflow tank to which the cleaning fluid overflows. The overflow tank is further provided with a circulation means for circulating overflown cleaning fluid again into the cleaning tank to change the flow rate of the cleaning fluid flowing via the flow port of the cleaning tank.
Moreover, there is provided a tray for use in a wafer cleaning device in which a plurality of wafers are arranged at predetermined intervals, conveyed into a cleaning tank of the wafer cleaning device by a conveying means, and cleaned. The tray comprises a band-shaped-peripheral wall surrounding an outer periphery of a plurality of arranged wafers to expose upper and lower portions of the wafers; grasping grooves formed in the peripheral wall for grasping opposite side ends of the wafers; an engaging portion for mounting the peripheral wall at a predetermined height from a bottom face of the cleaning tank; and grasping portions of the conveying means extended upward from front and back peripheral walls of the arranged wafers.